High silicon and high manganese steel



Patented Sept. 3, 1935 J UNITED s ArEs PATENT? OFFICE men SILICON .ANDmen MANGANESE STEEL' Abner C. Jones, Lebanon, Pa., assignor to LebanonSteel Foundry, Lebanon, Pa., a corporation of Pennsylvania No Drawing.

Original application November 7,

1930, Serial No. 494,192. Divided and this application November 24,1933, Serial No. 699,567

.3 Claims. (01. 75-'-1) This invention relates to steel products. Thisapplication is a division of my application, Serial No. 494,192, filedNovember 7-, v 1930, Patent -#1,94l,556 of January 2, 1934. Steelcastings may be obtained from the steel that is produced 3.00% ofmanganese, about 0.50% to 3.00% of sili- 0.06% each of sulphur and Voxide and gases, such as carbon monoxide and face area is exposed to themoist sand of tin? mold.

Such sections are apt to show considerable porosity or pinholes.

It has been found that. this trouble of porosity can be avoided by theaddition of aluminum to the molten steel, but the addition of suflicientaluminum to take care of this condition often results in decreasedductility of the steel. By the present invention, silicon-manganesesteel is produced having the desired physical properties in which thetrouble of porosity is obviated without the use of a deleterious amountof aluminum. The process is carried out so that the final product willcontain less than about 0.20% of carbon and in such a way that the steelis deoxidized and degasified during its production by carbon and theintroduction of silicon and manganese so that dissolved gases areremovedand castings free from porosity can be obtained.

The following is given as a specific example of practicing thisinvention, but it is to be understood that the proportions can be variedover a considerdized condition able range: Steel scrap of about 0.20% to0.30% carbon content is melted in an acid electric furnace. .Before thecharge is completely melted,

. sufiicient iron ore is introduced into the bath so that the carboncontent after the reaction brought about by the ore, will be about .12%After the charge is completely melted, a sufiiciept amount of silicasand is added to make the slag more siliceous and therefore lessoxidizing. This increases its ability to hold iron oxides and thusdecreases the amount of iron oxides in the bath metal. When thetemperature reaches the point where the carbon reacts with the dissolvediron oxides obtained from the ore additions, the bath boils due to theformationof carbon monoxide gas which passes through the slag and reactswith oxides therein. forming carbon dioxide and thus reduces the oxiofthe slag by decreasing its oxide content.

As the carbon gets lower to, say, about 0.12% in the molten bath, thereaction slows down due to the fact that the amounts of carbon and ironoxide in the bath decrease and the steel has a sufliciently greataflinity for the remaining carbon to prevent further reaction of thecarbon with the iron oxide in the bath. 7

When the boiling subsides, more carbonis added to the bath, preferablyin the fond of low silicon pig iron or wash metal, the latter being ironcontaining only about 4% of combined carbon. The carbon that is addedreacts with more of the iron oxide of the bath and the bath is rabbledafter the carbon is added to promote reaction between thecarbon and ironoxide. The amount of pig iron or other iron containing carbon is. about1%% of the molten batch. Additional reaction between carbon and ironoxide takes place using up about half of the added carbon which passesof! as a gas in the form of an oxide of carbon. At the same time, othergases thathiay be present in the molten batch are swept out mechanicallyand non-metallic impurities are carried off and rise and become part ofthe slag.

As soon as the second boiling subsides, which usually requires aboutfive or six minutes after the proper amount of pig iron or wash metalhas been added with the desired carbon content, about 1% or sixty poundsof low carbon silica-manganese per five thousand pounds of metal isadded and the bath rabbled for about a minute after the introductionofthe silico-manganese to distribute it uniformly throughout the bath. Theoxygen low bath of the electric furnace rise and enter pounds per squareinch, an elongation of 32.8%,

the slag and manganese silicate is also formed, which rises and entersthe slag. ,It has been found that the silicon content of the bath atthis stage will be about 0.50%.

About ten minutes is permitted for the siliconmanganese reaction to takeplace and exercise its cleansing effect upon'the bath and then thetemperature of the bath is slowly increased until the metal reachesapproximately the temperature that is suitable for pouring smallcastings care being exercised to prevent the steel from becoming'overheated.

After the temperature of the bath has been increased almostto thetemperature hot enough for pouring the castings, about 1 4% or seventypounds of silico-manganese. to five thousand pounds of metal is added,together with an equal amount of 50% ferro-si licon. The amount ofsillco-manganese and ferro-silicon introduced at this stage can bevaried considerably, depending upon the final composition that isdesired. The

bath is rabbled about a minute after the last addition to distribute thesilicon and manganese throughout the steel and the furnace is tappedabout two 'minutes after rabbling. By having the silicon and manganesedistributed throughout the steel, very little, if any, iron oxide isformed when themolten metal passes from the furnace into the ladle, asoxygen from the air combines with the manganese and silicon rather thanwith the iron. If desired, an additional amount of silicon may beintroduced into the ladle. The amount of silicon introduced into theladle should not exceed more than about 2% of the charge by'weightbecause of the danger of ,chilling the steel. The presence of-thesilicon and manganese not only helps to prevent the formation of poundsper square inch, a yield point of 53,000

a reduction of area of 64.7% and withstood a bend test of around a pinone inch in diameter. As an additional insurance against unusualconditionsof the mold that might result in porous castings, a smallamount of aluminum may be introduced into the ladle after it has beenfilled, without changing the physical propertiesof the steel very much.

By this invention steel is made that has a low carbon content and a highsilicon and high manganese content which can be poured into green sandmolds to produce small size castings that are free from porosity. Thesteel is very ductile with high tensile strength and high ratio of yieldpoint and .elastic limit to tensile strength.

Ferro silicon and low carbon manganese can be substituted forsilico-manganese, but the best results were obtained withsilico-manganese.

I claim:

1. Steel of high tensile strength and ductility containing about0.12%;carbon, 1.76% silicon, 1.53% manganese, less than 0.06% of sulphurand phosphorouseach, and the remainder substantially all iron, saidsteel being capable of being cast into green sand molds when meltedwithout becoming porous when it freezes.

2. Steel of high tensile strength and ductility containing about 0.12%carbon, about 1.76% silicon, about 1.53% manganese, lws than 0.06% ofsulphur and phosphorous each, and the remainder substantially all iron,said steel being capable of being cast into green sand molds when meltedwithout becoming porous when it freezes, said steel having a tensilestrength over 75,000 pounds per square inch.

3. Steel of high tensile strength and ductility ABNER c JONES.

